P1- Waves

P1- Waves

1. THE NATURE OF WAVES

   • We use waves to transfer energy and information. The direction of travel of the wave is the direction in which the wave transfers energy.
   • Different types of waves:
     • TRANSVERSE WAVE- The oscillation(vibration) of the particles is perpendicular(at right angles) to the direction in which the wave travels.
     • LONGITUDINAL WAVE- Oscillations of the particles is parallel to the direction of the wave. They are made up of compressions and rarefactions. Sound waves are longitudinal.
     • ELECTROMAGNETIC WAVES- (light and radio waves) They can travel through a vacuum. There are no particles moving in and electromagnetic wave, as these waves are oscillations in electric and magnetic fields. The oscillations are perpendicular to the direction of travel of the wave. So all electromagnetic waves are transverse waves.
     • MECHANICAL WAVES-(waves on a spring, sound waves) They travel through a medium substance. Mechanical waves may be transverse or longitudinal.

2. MEASURING WAVES

   • The AMPLITUDE of a wave is the height of the wave crest or the depth of the wave trough from the position at rest. The greater the amplitude the more energy it carries.
   • The WAVELENGTH of a wave is the distance from one crest to the next crest, or from one trough to the next.
   • The FREQUENCY of a wave is the number of wave crests passing a point in one second. Frequency is in herts(Hz). This unit is equivalent to per second(s).
   • The SPEED of a wave is given by the equation v= f x λ
     • V= wave speed in m/s. F= frequency in Hz. λ= wavelength in m.
   • The diagram shows a transverse wave but the same apply to a longitudinal wave.
   • The wavelength of a longitudinal wave is the distance from the middle of one compression to the middle of the next compression. This is the same for rarefactions.
   • The frequency of a longitudinal wave is the number of compressions passing a point in 1 second.

3. WAVE PROPERTIES- REFLECTION

   • The images seen in a mirror is due to the reflection of light.
   • The diagram shows how an image is formed by a plane(flat) mirror. The incident ray is the ray that goes towards the mirror. The reflected ray is the ray coming away from the mirror.
   • We draw a line called he normal, perpendicular to the mirror at the point where the incident ray hits the mirror.
   • The angle of incidence is the angle between the incident ray and the normal.
   • The angle of reflection is the angle between the reflected ray and the normal. For any reflected ray the angle of incidence is equal to the angle of reflection.
   • The image in a plain mirror is: -the same size as the object, upright, same distance behind the mirror as the object is in front, virtual.
   • A REAL IMAGE is one that can be formed on a screen, because the rays of light that produce the image actually pass through it.
   • A VIRTUAL IMAGE cannot be formed on a screen, because the rays of light that produce the image only appear to pass through it.

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